Albert the Bear (German: Albrecht der Bär; Latin: Adelbertus, Adalbertus, Albertus; c. 1100 – 18 November 1170) was the first Margrave of Brandenburg (as Albert I) from 1157 to his death and was briefly Duke of Saxony between 1138 and 1142.

Albert's entanglements in Saxony stemmed from his desire to expand his inherited estates there. After the death of his brother-in-law, Henry II, Margrave of the Nordmark, who controlled a small area on the Elbe called the Saxon Northern March, in 1128, Albert, disappointed at not receiving this fief himself, attacked Udo V, Count of Stade, the heir, and was consequently deprived of Lusatia by Lothar. Udo, however, was said to have been assassinated by servants of Albert on 15 March 1130 near Aschersleben. In spite of this, he went to Italy in 1132 in the train of the king, and his services there were rewarded in 1134 by the investiture of the Northern March, which was again without a ruler.

The seal of Albert the Bear.

In 1138 Conrad III, the Hohenstaufen King of the Germans, deprived Albert's cousin and nemesis, Henry the Proud of his Saxon duchy, which was awarded to Albert if he could take it. After some initial success in his efforts to take possession, Albert was driven from Saxony, and also from his Northern march by a combined force of Henry and Jaxa of Köpenick, and compelled to take refuge in south Germany. When peace was made with Henry in 1142, Albert renounced the Saxon duchy and received the counties of Weimar and Orlamünde. It was possibly at this time that Albert was made Archchamberlain of the Empire, an office which afterwards gave the Margraves of Brandenburg the rights of a prince-elector.

Once he was firmly established in the Northern March, Albert's covetous eye lay also on the thinly populated lands to the north and east. For three years he was occupied in campaigns against the Slavic Wends, who as pagans were considered fair game, and whose subjugation to Christianity was the aim of the Wendish Crusade of 1147 in which Albert took part. Albert was a part of the army that besieged Demmin. And at the end of the war, recovered Havelberg, which had been lost since 983. Diplomatic measures were more successful, and by an arrangement made with the last of the Wendish princes of Brandenburg, Pribislav of the Hevelli, Albert secured this district when the prince died in 1150. Taking the title "Margrave in Brandenburg", he pressed the "crusade" against the Wends, extended the area of his mark, encouraged German migration, established bishoprics under his protection, and so became the founder of the Margraviate of Brandenburg in 1157, which his heirs — the House of Ascania — held until the line died out in 1320.

In 1164 Albert joined a league of princes formed against Henry the Lion, and peace being made in 1169, Albert divided his territories among his six sons. He died on 13 November 1170, possibly in Stendal, and was buried at Ballenstedt.

Albert's personal qualities won for him the cognomen of the Bear, "not from his looks or qualities, for he was a tall handsome man, but from the cognisance on his shield, an able man, had a quick eye as well as a strong hand, and could pick what way was straightest among crooked things, was the shining figure and the great man of the North in his day, got much in the North and kept it, got Brandenburg for one there, a conspicuous country ever since," says Carlyle, who called Albert "a restless, much-managing, wide-warring man." He is also called by later writers "the Handsome."